I. Field of the Invention
This invention is directed generally to intravascular catheters, and more particularly to the design of a dilatation catheter having a pair of associated fluidcarrying tubes, the operative or distal end of one of which supplies fluid to inflate an expansible balloon and the operable or distal end of the other of which supplies an injectable dye or contrast enhancing fluid adjacent the proximal end of the balloon.
II. Description of the Related Art
Dilatation catheters of the general class of the present invention are well known and generally described in references such as the American Journal of Cardiology, Volume 49, Apr. 1, 1982, pages 1216-1222. They are basically employed to enlarge constrictions in larger vessels or arteries, or even other internal cavities by employing a precisely placed inflatable balloon device to compress plaque or other obstructing material against the arterial wall or the outer surface of the cavity of interest thereby reopening a larger channel for blood flow or the like. This method of treatment of stenotic lesions in the vascular system is known as transluminal balloon angioplasty. The procedure involves the use of an elongated, flexible, plastic catheter having an inflatable expander member or balloon proximate its distal tip. The catheter describes a tubular lumen suitable to conduct an amount of fluid introduced from without the body to and from the balloon to accomplish inflation and deflation of the balloon as required. One such device is illustrated and described in U.S. Pat. No. 4 762 129. The system is introduced at an appropriate site in the vascular system, commonly in the femoral artery, and routed through the system using a guide wire to the site of the lesion of interest to be treated. Once the deflated balloon is positioned in the desired relationship to the lesion, the appropriate fluid is introduced into the proximal end of the catheter and flows to inflate the balloon which, in turn, compresses the stenotic lesion against the wall of the blood vessel.
In order for the balloon to be precisely positioned with respect to the stenosis to be compressed and the result easily evaluated, a contrast medium or dye is utilized to enhance the contrast at the site so that the scene can be viewed with greater resolution by the operator of the device. Normally, this involves injecting an amount of contrast fluid or dye material into the femoral artery and waiting until the diluted dye makes its way through the vascular system to the site of the stenotic lesion. There is a significant time delay between the time of injection and the corresponding effect on the image viewed on the fluoroscope. Because of the dilution effect, it also requires the injection of an additional amount of fluid consistent with the need to circulate the fluid through the vascular system to the site. Adjustments in concentration also require time and may lack the desired accuracy or control. It would represent a great improvement in the art if the appropriate contrast fluid or dye could be introduced near the distal end of the catheter proximate to the balloon member and the stenotic lesion. This would save a great deal of the time spent waiting for the fluid to circulate, reduce the amount of contrast fluid required and increase the control over the predictable result of dye addition.